Purpose: The goal of the present study was to evaluate the outcome of risk-adapted planning treatment volumes (PTVs) in patients with cervical lymph node metastases of unknown primary cancer (UPC) treated with intensity-modulated radiotherapy (IMRT). Patients and material: Between January 2006 and November 2012, 28 patients with cervical lymph node metastases of UPC were treated in our institution with IMRT either postoperatively (n = 20) or as definitive treatment (n = 8). Nodal involvement distributed as follows: N1 (n = 2), N2a (8), N2b (10), N2c (4), and N3 (4). Systemic therapy with cisplatin or cetuximab was added concomitantly in 20 of 28patients (71 %). Radiotherapy using simultaneously integrated boost (SIB-IMRT) was carried out with 2.0 or 2.11Gy single doses up to 66/70Gy. Results: Mean/median follow-up was 31.6/30.5months (range 3-78months). In all, 15 of 28patients were treated with unilateral SIB-IMRT (54 %). An elective PTV to the contralateral oropharynx and contralateral levelII-III lymph nodes was carried out in 8patients with PET-CT suspected but not histologically proven involvement, recurrences or former tumor of the oropharynx. More extended treatment fields were reserved for patients with N2c or bilaterally N3 status (n = 5). The 3-year overall survival, mucosal control, neck control and distant metastasis-free survival rates were 76, 100, 93, and 88 %, respectively. No patient suffered from a locoregional recurrence. Two patients treated with radiotherapy alone had persistent nodal disease. No gradeII or higher late sequel has been observed. Conclusion: Our single center approach to treat patients with cervical lymph node metastases of UPC with individualized, risk-adapted SIB-IMRT resulted in high locoregional tumor control and was well tolerated
